<!DOCTYPE html>
<html lang="zh">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .list li>ul {
            background-color: lightgray;
        }

        .list li:hover * {
            color: blue;
        }
    </style>
</head>

<body>
    <ul class="list">
        <li>Item 1
            <ul>
                <li>Subitem 1</li>
                <li>Subitem 2</li>
            </ul>
        </li>
        <li>Item 2
            <ul>
                <li>Subitem 3</li>
                <li>Subitem 4</li>
            </ul>
        </li>
    </ul>
</body>

</html>